Seldon Core and KFServing both have features for traffic-splitting. For this they rely on a Gateway.
Currently Seldon Core supports Istio or Ambassador. KFServing currently only supports Istio.
Detector components and KFServing both also use Knative. That requires one of requires one of Ambassador, Contour, Gloo, Istio, Kong or Kourier
Seldon Deploy itself does not have a hard dependency on Istio. It has dependencies on components that use Istio.
Seldon Deploy can be used to make predict calls to models. The gateway affects the form of the urls to the models. However, this is configurable in the Seldon Deploy values file using templating to set the form of the url from relevant parameters. It defaults to Istio.
The key issues to consult on the upstream projects are the below - the Knative one at the top explains the situation well:
https://github.com/knative/serving/issues/10417 https://github.com/SeldonIO/seldon-core/issues/2988 https://github.com/SeldonIO/seldon-core/issues/416 https://github.com/SeldonIO/seldon-core/issues/1129
Please comment on the above or otherwise contact Seldon if this is of interest.